Abstract
Seven trichodorid species including a new one (Trichodorus hangzhouensissp. nov., T. nanjingensis, T. pakistanensis, T. cedarus, Paratrichodorus porosus, Nanidorus renifer and N. minor) were recovered from the rhizosphere of different hosts in 13 provinces of China. Each of the recovered species was characterized based on morphology and molecular data using rRNA gene sequences. Trichodorus hangzhouensissp. nov. is characterized by its males having medium-sized onchiostyle (46–49 µm) and three ventromedian cervical papillae (CP) anterior to the secretory-excretory (S-E) pore, CP1 located opposite the anterior part of isthmus, S-E pore opposite the isthmus or anterior end of pharyngeal bulb, spicules slightly ventrally curved, relatively small, 33.2 (32.0–34.5) µm long, wider slightly marked capitulum, lamina partially striated without bristles at striation; and females having rounded triangular sclerotized vaginal pieces with tips directed towards vulva, 1.5–2.0 µm sized, at about 1 µm apart, vulva pore-like in ventral view. Phylogenetic analysis based on D2-D3 28S rRNA gene sequences differentiated the new species among Trichodorus species from Europe, Asia and USA which formed a large clade. A review of the distribution of Trichodorus, Nanidorus and Paratrichodorus species revealed that T. cedarus, T. nanjingensis, T. pakistanensis and P. porosus are the most widespread species recorded from different provinces of China. This is the first extensive study of trichodorid species occurring in China.
Highlights
Stubby root nematodes of the family Trichodoridae Thorne, 1935 are polyphagous root ectoparasites and have a global distribution (Decraemer and Robbins 2007)
Some of the species have the ability to transmit plant pathogenic viruses (e.g., Tobacco Rattle Virus (TRV), Pea Early Browning Virus (PBV) and Pepper Rinspot Virus (PRV)) which has stimulated experts to focus on the family Trichodoridae (MacFarlane et al 2002, Decraemer et al 2013, 2019)
The objectives of the present study are to: i) characterize morphologically and molecularly recovered trichodorid species including one new Trichodorus species; ii) evaluate the phylogenetic relationships of the new species with other members of the genera based on their 18S rRNA, D2-D3 expansion domain of 28S rRNA and ITS2 of rRNA gene sequences and iii) summarize the geographic distribution of Trichodorus, Nanidorus and Paratrichodorus species in China, in addition, providing a comprehensive list of the past records and present findings of trichodorid nematodes
Summary
Stubby root nematodes of the family Trichodoridae Thorne, 1935 are polyphagous root ectoparasites and have a global distribution (Decraemer and Robbins 2007). They cause damage to a wide range of crops and natural vegetation by directly feeding on root hairs and epidermal cells. In recent years several nematologists have successfully applied rRNA genes sequence (18S, 28S, and ITS) analyses for studying the phylogenetic relationships of trichodorid species (Duarte et al 2010, Zhao et al 2013, Pedram et al 2015, 2017, Decraemer et al 2019). The importance of sequence-based studies for species identification and the lack of molecular data of known species from China has led us to compile a detailed report of trichodorids occurring in the country
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